The disclosed embodiments of the present invention relate to three-dimensional (3D) image/video playback, and more particularly, to a method of identifying a view order of image frames of a stereo image pair according to image characteristics and related machine readable medium thereof.
With the development of science and technology, users are pursing stereoscopic and more real image/video display rather than high quality image/video display. There are two techniques of present stereo image/video display. One is to use a display apparatus, which collaborates with glasses (such as anaglyph glasses, polarization glasses or shutter glasses), while the other one is to use only a display apparatus without any accompanying glasses. No matter which technique is utilized, the main theory of stereo image/video display is to make the left eye and the right eye see different images, thus the brain will regard the different images seen from two eyes as stereo images.
More and more 3D contents are produced and many of them are available from Internet. In the meantime, there are many co-existing formats to store 3D contents. For example, the available 3D formats include horizontal interlaced, checkerboard, over-under, etc. An Internet television (TV) can view image or video contents directly from Internet. In order to support playback of 3D contents, the Internet TV should have the capability of detecting 3D formats.
Some video standard such as Motion Picture Experts Group (MPEG) has newly added support for some 3D formats through tagging. The High-Definition Multimedia Interface (HDMI) 1.4 interfaces also support many popular 3D formats. However, not all popular 3D formats are supported by MPEG standards or HDMI 1.4 interfaces. Most 3D contents on Internet use different kinds of 3D formats, and do not support above MPEG and HDMI 1.4 standards. Besides 3D videos, there exist a large amount of 3D images, which do not have standard ways to store 3D format information in different image types. Hence, the Internet TV needs to automatically distinguish between 2D and 3D image/video contents, and determine 3D formats for 3D contents. The conventional methods can detect 3D formats, but cannot know the view order of image frames in a stereo image pair. That is, the conventional 3D format method does not know which one of the image frames in the stereo image pair is a left view (i.e., a left-eye image frame) and also does not know which one of the image frames in the stereo image pair is a right view (e.g., a right-eye image frame).
It is interesting that most people can see 3D effects even when the playback order of the left view and the right view are switched. However, the 3D effects they perceived are generally weird and will cause eye fatigue quickly. Specifically, it is difficult to identify left or right views since most people can perceive 3D effects from switched left and right views. Mathematically, the operation of switching left and right views changes signs of mathematic formulae. For 3D effects, it means that depth values change signs. That is, close objects will appear far away, and far objects will appear close. However, the sizes of objects in both views are not changed from the switching. The perceived 3D effects are weird since the perceived depth values hint that smaller objects are closer, while the object sizes hint that smaller objects should be further away. Such contradiction of hints will cause eyestrain very fast.
For some 3D formats such as checkerboard pattern, the order to arrange left or right views is specified, while most others are not. There are also no generally accepted rules for the arrangement. As a result, many 3D software packages have the option to arrange the view order of the left view and the right view according to user's preference. As mentioned above, one way to distinguish the left and right views is to tag this information in video files as defined by some standards. Another way is to set it manually by the user, as current software 3D players do. These two kinds of methods apparently are not suitable for viewing 3D video/image contents on Internet from an Internet TV.
Thus, to make 3D viewing experience pleasant, it is important not only to detect the correct 3D format for 3D contents, but also to identify the correct view order of the left and right views.